I know full well it can be devastating to loose a pet you had a close bond with and for that, I am sorry.
Take the time you need to grieve and understand that dying is a natural part of living,now your pets life is complete.
You will never forget your pet, that will keep your pet alive in memory.
I know I was just devastated when my mouse I had a very strong bond with died quietly in his sleep, just seemed so sudden in spite of living very long for a mouse, I never considered that. I have had numerous small pets since, all come and gone and I still remember my Yogi like yesterday. Yogi died in 1963 if that says anything.
All I can say is so sorry for your loss. Time will heal the hurt.